C Program to Calculate the Sum of Odd & Even Numbers

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This is a C program to find the sum of odd and even numbers from 1 to N.

Problem Description

The program takes the number N and finds the sum of odd and even numbers from 1 to N.

Problem Solution

1. Take the number N upto which we have to find the sum as input.
2. Using for loop take the elements one by one from 1 to N.
3. Using if,else statements separate the element as even or odd.
4. Add the even and odd numbers separately and store it in different variables.
5. Print the sum separately and exit.

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Program/Source Code

Here is source code of the C program to calculate the sum of odd & even numbers. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

  1.  
  2. #include <stdio.h>
  3.  
  4. void main()
  5. {
  6.     int i, num, odd_sum = 0, even_sum = 0;
  7.  
  8.     printf("Enter the value of num\n");
  9.     scanf("%d", &num);
  10.     for (i = 1; i <= num; i++)
  11.     {
  12.         if (i % 2 == 0)
  13.             even_sum = even_sum + i;
  14.         else
  15.             odd_sum = odd_sum + i;
  16.     }
  17.     printf("Sum of all odd numbers  = %d\n", odd_sum);
  18.     printf("Sum of all even numbers = %d\n", even_sum);
  19. }
Program Explanation

1. User must first enter the number upto which he/she wants to find the sum and is stored in the variable num.
2. Using for loop take the elements one by one from 1 to num.
3. Use if,else statement for each element to find whether it is odd or even by dividing the element by 2.
4. Initialize the variables odd_sum and even_sum to zero.
5. If the element is even,then increment the variable even_sum with the current element.
6. If the element is odd,then increment the variable odd_sum with the current element.
7. Print the variables odd_sum and even_sum separately and exit.

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Runtime Test Cases
Case 1:
Enter the value of num
10
Sum of all odd numbers  = 25
Sum of all even numbers = 30
 
Case 2:
Enter the value of num
100
Sum of all odd numbers  = 2500
Sum of all even numbers = 2550

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Here’s the list of Best Reference Books in C Programming, Data-Structures and Algorithms

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If you wish to look at other example programs on Simple C Programs, go to Simple C Programs. If you wish to look at programming examples on all topics, go to C Programming Examples.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn